Method of investigating well blast impingement conditions



May 5, 1970 w. FQBALDWIN L 3,509,764

METHOD OF INVESTIGATING WELL BLAST IMPINGEMENT CONDITIONS Filed July 5, 1968 [$9 .55 FILTER 1 CRO 42. 52 RECTIFIER 2|O6 I J 47 Fig. 2

INVENTORS W/l/ef/ E Baldwin BY Wayne M /VeBIy AGENT United States Patent 3,509,764 METHOD OF INVESTIGATIN G WELL BLAST IMPINGEMENT CONDITIONS Willett F. Baldwin, Dallas, Tex., and Wayne E. McNeely,

Morgan City, La., assignors to Mobil Oil Corporation,

a corporation of New York Filed July 5, 1968, Ser. No. 742,670 Int. Cl. E21b 47/10 U.S. Cl. 73155 7 Claims ABSTRACT OF THE DISCLOSURE The specification discloses a method of investigating blast-impingement conditions of a multiply completed well. A sound detector is lowered into the tubing string extending through a producing zone. As the sound detector is moved longitudinally adjacent the producing zone, the ambient sound intensity profile is monitored. Impingement of well stream on the exterior of the tubing string creates sound waves which result in fluctuations of the sound intensity profile.

BACKGROUND OF THE INVENTION In petroleum wells, tubing strings often extend through a producing zone where production streams flow into the well through perforations in the well casing. This is particularly frequent in multiply completed wells which are designed for production from several vertically spaced producing zones. In a conventional dual completion well, for example, a long tubing string extends from the mouth of the well through a packed-off upper producing zone to a lower producing zone; and a short tubing string extends from within the packed-off upper producing zone to the mouth of the well. With this arrangement both the upper and lower producing zones may produce through their respective tubing strings without intercommunication.

In multiply completed wells a serious problem is caused by the continuous impingement of well stream from an upper producing zone onto the exterior of a long tubing string extending through the upper zone to a lower producing zone. The well stream may flow through perforations in the casing in the form of high velocity jets. The impingement of these jets on the long tubing string, which is known as the blast effect, results in abrasion and erosion of the tubing string until ultimately failure occurs and a hole is created. The well stream flowing through the perforations is often laden with sand, silts, clays, and other formation materials which aggravate the blast effect and quicken failure of the long tubing string.

Sometimes all but a few of the perforations in an upper producing zone may become clogged while the total well flow remains constant. This means that fiow through the unclogged perforations is probably at excessive velocity. If it were known that well flow was through only a few perforations, steps could be taken to control the reservoir to maintain the well stream velocity impinging on the tubing below known critical rates.

The state-of-the-art technique for detecting blast conditions is by visual observation at the surface of formation materials, such as sand, that appear in the well production. By this time, of course, failure of the produetion tubing has occurred and generally any remedial action short of well workover is futile. Replacement of the destructed tubing string often costs hundreds of thousands of dollars, particularly in offshore wells.

SUMMARY OF THE INVENTION The present invention provides a new technique for detecting and diagnosing blast effect conditions in a well 3,509,764 Patented May 5, 1970 prior to tubing failure with the subsurface well equipment in place. By the present invention a sound detector is positioned inside a tubing string to detect the sound created by the impingement of well stream on the exterior of the tubing string. The sound detector may be lowered into the tubing by a cable from the earths surface. As the sound detector is moved longitudinally through the tubing adjacent a producing zone to be investigated, the ambient sound intensity profile is monitored. The sound created by impingement of the well stream on the tubing will cause fluctuations in the sound intensity profile.

The sound intensity profile may be correlated with precompletion data to yield information as to the precise location of blast impingement, the velocity of blast impingement, and perhaps the type of materials laden in the impinging stream, as well as the components of the well stream itself.

In a preferred embodiment of the invention, the sound detector comprises an electroacoustic transducer encased in a subsurface logging tool adapted to pass through a tubing string. The logging tool is suspended by a wireline which transmits signals to surface recording equipment and conveys electrical power to the subsurface logging tool. The electrical signal generated by the transducer in the logging tool is rectified and the amplitude of the rectified signal is recorded as a function of depth of the logging tool in the well. Electrical wave filtering may be provided to suppress background noise frequencies which are not pertinent to the impingement of the well stream on the tubing string.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a dual completion well and the technique of logging according to one embodiment of the present invention; and

FIG. 2 is a block diagram of one form of surface recording.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS Referring to the drawing there will now be described in detail certain specific embodiments of the invention.

In FIG. 1 a wellbore 10 is shown extending from the earths surface at 12 through an upper producing zone 14 an a lower producing zone 16. A casing 18 is shown anchored by a cement sheath 20 to wellbore 1-0. A tubing string (the short string) 22 extends from the mouth of the well into the casing 18 near the upper producing zone 14. Another tubing string( the long string) 23 extends from the mouth of the well through the upper producing zone 14 to the lower producing zone 16. A dual packer 24 and a single packer 26 seal off the upper producing zone 14. Perforations 28 and 29 are shown respectively in producing zones 14 and 16.

The upper producing zone 14 is in fluid communication with the short tubing string 22. Petroleum, such as oil or gas, flows through perforations 28 and through the short tubing string 22 to surface tanks or pipelines. Similarly, the well stream from the lower producing zone 16 flows through perforations 29 and through the long tubing string 23.

As described above, the blast effect results when the Well stream, which is often sand laden, flows through perforations 28 in the form of high velocity jets and impinges upon the exterior of tubing string 23. When tubing string 23 fails under blast conditions, at least a part of the well stream from producing zone 14 flows into tubing string 23 and is mixed with the well flow from the lower producing zone 16.

In carrying out the present invention, the lower producing zone 16 is preferably shut in by conventional means not shown so that no well flow passes through tubing string 23. The upper producing zone 14 is preferably maintained at normal production so that the blast effect of well stream on tubing string 23 may be investigated under normal operating conditions. A sound detector is inserted into tubing string 23 and lowered by means of a cable .32. Cable 32 is a wireline which includes conductors for transmitting electrical power to sound detector 30 and conveying the detected signals to surface recording equipment. Cable 32 is shown wound around a reel 35 and passing over a sheave 33 fixed to a support 34. This arrangement permits moving sound detector 30 longitudinally inside tubing string 23.

In one mode of operation, sound detector 30 is positioned at a number of points along the producing zone 14; and at each point while the sound detector is stationary the intensity of the sound created by the impingement of well stream onthe exterior of tubing string 23 is monitored. In another mode of operation, sound detector 30 is moved continuously inside tubing string 23 and sound intensity is monitored continuously. Regardless of the mode of operation, the detected sound intensity profile is preferably recorded in correlation with the depth of sound detector 30 in the well.

Sound detector 30 is shown encased in a subsurface logging tool which may be of conventional construction. This logging tool includes bumpers or centralizers 38 which keep the logging tool centrally located in the tubing string and reduce any background noise created by the scraping or banging of the tool inside the tubing string.

Sound detector 30 comprises an electroacoustic transducer of conventional acoustic logging tool design with a radial response pattern. Such a transducer may be of the piezoelectric type, such as lead zirconate material, formed in the shape of a right circular cylinder.

FIG. 2 illustrates in block diagram one form of surface recording equipment. The electrical signal from sound detector 30 is amplified by means in the logging tool and conducted through a surface amplifier 40 and rectifier circuit 42 to a strip chart recorder 44. Rectifier circuit 42, which may be of the full wave or half wave type, eliminates the negative-going excursions in the detected signal.

Strip chart recorder 44 is of the conventional type used with ordinary acoustic logging equipment. It includes a moving pen or recording element 45 and a recording medium such as paper 46. The recording medium 46 is moved relative to recording pen 45 in correlation with the depth of the sound detector 30 by means of an electromechanical link 47 coupled to the sheave 33 over which cable 32 passes.

As the sound detector 30 is moved along the tubing string 34, recorder 44 produces a log or trace of the amplitude of the sound detected. The recording medium 46 is driven at a rate correlated with the movement of the sound detector and the recording pen 45 moves transversely in proportion to the amplitude of the rectified detector signal. Fluctuations in the amplitude of the log produced by recorder 44 may be correlated with impingement of well stream on tubing string 23.

If desired, an electrical filter 48 may be placed in circuit with the recording equipment by operation of switches 49 and 50. Filter 48 may be used to suppress background noise frequencies unrelated to the impingement of well stream on tubing string 23. Filter 48 may be of any type, such as low pass, high pass, or band pass. Filter 48 may be manually adjustable so that the effect of filtering can be varied to suit different blast effect or noise conditions.

The waveform of the detected signal is shown visually displayed on a cathode ray oscilloscope 51. The detected signal is applied to the vertical deflection plates of oscilloscope 51. An arbitrary time base generated within oscilloscope 51 is applied to the horizon al d fl q on p 4 As filter 48 is adjusted the effect on the detected waveform may be observed visually on oscilloscope 51.

The depth of the sound detector in the wellbore is indicated visually by a depth readout device 52 coupled by an electromechanical link 53 to sheave 33. At points along the tubing string at which high sound intensity is shown by the strip chart log, special attention may be given to the adjustment of filter 48 and the resultant effect of the detected Waveform observed on oscilloscope 51. Photographs may be taken of the waveform depicted on oscilloscope 51 for later study and analysis.

Other types of indication or recording of the detected sound may be employed. For example, the intensity of the detected signal may be displayed on a meter and the visual meter readings may be recorded in correlation with depth of the sound detector. Furthermore, the intensity of the sound may be indicated aurally 'by any suitable means, such as a pair of earphones Worn by an operator. By listening to the audio sound created by the impingement of the well stream, an operator may deduce information about blast conditions.

The detected sound may be recorded magnetically for later playback or visual readout. By magnetically recording the detected sound, the signal may be fed to a computer for frequency analysis or signal enhancement.

Various types of measurements of the amplitude of the detected sound signal are suitable. For example, where the impingement of well stream on a tubing string is at substantially constant velocity so that a steady state condition results, a peak measurement may be taken of the amplitude of the detected signal. Alternatively, any of the various time measurements may be made, such as average amplitude or root means square amplitude.

Some of the recording equipment illustrated in FIG. 2 may be located in the subsurface logging tool. For example, the rectifier 42 could be located in the subsurface logging tool so that only the rectified signal would be transmitted to the surface.

Now that several specific embodiments of this invention have been described, it will be apparent to those skilled in the art that still other embodiments may be made still within the true spirit and scope of the invention. It is intended to cover all such embodiments as fall within the scope of the appended claims.

The invention claimed is:

1. A method of investigating a multiply completed cased well including a tubing string extending through an upper producing zone to produce from a lower producing zone, comprising the steps of:

(a) positioning a sound detector inside the tubing string adjacent the upper producing zone, and

(b) while producing from the upper producing zone, monitoring with said sound detector the sound created by the impingement of well production stream from the upper producing zone on the exterior of the tubing string.

2. The method as defined by claim 1 including the steps of:

(a) locating said sound detector at a number of longitudinal points in the tubing string adjacent the upper producing zone; and

(b) recording a signal proportional to the amplitude of the sound detected at each of said points in correlation with the depth of said sound detector in the Well.

3. The method as defined by claim 1 further comprising the step of:

filtering the detected sound to suppress background noise frequencies unrelated to the impingement of well production stream on the exterior of the tubing string.

4. A method of investigating a multiply completed cased well including a tubing string extending through an upper producing zone to produce from a lower pro-1 ducing zone, comprising the steps of:

(a) moving a sound detector longitudinally inside the tubing string adjacent the upper producing zone; and

(b) while producing from the upper producing zone with the lower producing zone shut in, monitoring the ambient sound intensity profile with said detector, whereby impingement of Well stream from the upper producing zone on the exterior of the tubing string results in fluctuations in the sound intensity profile.

5. A method of investigating a multiply completed,

cased Well including a tubing string extending through an upper producing zone to produce from a lower producing zone, comprising the steps of:

(a) producing from the upper producing zone in the normal manner;

(b) shutting in the production of the lower producing zone;

(c) lowering a sound detector into the tubing string by means of a cable from the earths surface;

(d) moving said sound detector inside the tubing string adjacent the upper producing zone and detecting the sound intensity created by the impingement of well production stream on the exterior of the tubing string; and

(e) making a record of the detected sound intensity.

6. A method of investigating a multiply completed,

cased well including a tubing string extending through an upper producing zone to produce from a lower producing zone, comprising the steps of:

(a) producing from the upper producing zone in the normal manner;

(b) shutting in the production of the lower producing zone;

(c) lowering a sound detector into the tubing string by means of a cable from the earths surface;

(d) locating said sound detector inside the tubing string adjacent the upper producing zone and detecting the sound created by the impingement of well production stream on the exterior of the tubing string; and

(e) making a record of a characteristic of the detected sound.

7. The method of claim 6 wherein said characteristic of the detected sound is recorded as a function of depth.

References Cited UNITED STATES PATENTS 8/1940 Kinley. 3/1946 Walstrom 73-151 X 5 JERRY W. MYRACLE, Primary Examiner 

